1. Field of the Invention
This invention relates generally to a flow regulation apparatus and, more particularly, to a check valve which will open at very low pressures to permit fluid flow in a first direction and which will close to prevent flow in a second direction with extremely low back flow leakage while withstanding high back pressures, and which is not sensitive to the position or orientation of the valve.
2. Description of the Prior Art
One requirement of one way flow or check valves, such as the type used in medical fluid flow lines, is that the valves offer little resistance to fluid flow in one direction and stop fluid flow in the opposite direction with low back flow leakage. A valve which is commonly used for this purpose is a duckbill valve which comprises a pair of valve lips which readily open at low forward flow pressures and which readily close to prevent back flow in an opposite direction. While this type of valve provides an effective mechanism for controlling fluid flow, they typically cannot withstand high back pressure if they are designed for low opening and forward pressure. Also, the assembly of duckbill valves into a housing typically requires care to ensure that the valve is properly oriented and aligned relative to the ends and sides of the housing in order ensure effective operation.
Another form of known check valve uses a disc shaped regulator element which is generally required to be centered within a housing. Reliable operation of the regulator element in such valves is sensitive to the precise centering of the regulator element within the valve housing and, in addition to requiring care in properly placing the regulator element in the valve housing during assembly, prior art regulators have been subject to misalignment by slipping off center during use, leading to unacceptable leakages of the valve. In addition, some disc valve designs are position sensitive and consequently also subject to failure or leakage.
While known check valves of the above described type and other check valve designs provide satisfactory operation for many applications, there is a continuing need for a check valve which reliably responds to permit fluid flow at low pressures, as well as preventing back flow with extremely low leakage of fluid, and which is of a simplified construction permitting ease of assembly, including automated assembly of the valve structure.